Microwave integrated circuits generally comprise a circuit including passive and active components and interconnecting leads mounted on the upper surface of a substrate with a metal layer or film on the lower surface serving as a heat sink and/or path to ground. It is often desirable to create direct connections between specific points of the circuit on the upper surface and the lower surface metal either to form a low inductance/low resistance conductive path to ground and/or to provide a heat conductive path to the lower surface metal, specifically in the vicinity of active devices. In the present state of the art when the substrate used is a ceramic substrate, such connections are typically obtained by cutting holes, referred to as "via holes" or "vias", through the substrate and by metallizing the walls of the hole to provide a conductive connection between the top and bottom of the holes. The holes may be cut either before or after processing of the substrate. In the first case, the presence of holes significantly hinders the photolithography processes used in the formation of the microwave circuits and their electrical interconnection typically preventing the definition of fine detail in the neighborhood of a hole. In the second case, the hole cutting process is severely limited by the need to preserve the integrity of the circuit which has already been fabricated. This is especially true in the case of ceramic substrates such as alumina where holes cannot be easily etched chemically and have to be drilled mechanically or by laser.